This map shows higher zones than the accepted USDA map allows for - the USDA hardiness zone map simply assigns Zone 11 for anywhere with an average annual minimum temperature above 40 F. If they are following the zone system, then each zone is 10F higher than the last one, making Zone 12 at 50 F and Zone 13 at 60 F.

This hardiness zone map from the Australian National Botanic Gardens represents a modified version of the USDA zones, because, as the website says, "This is because Australia, in winter, is much warmer than most of North America in winter, so the lowest US zones aren't needed. All of Australia (excluding Macquarie Island) is covered by just over four US zones (7b to 11). To make the map more useful to Australians I have created 7 zones to fit our climatic range and used metric units."

Canada is doing an ambitious project and needs your help! As they explain on their site, "Our aim is to go beyond a single general map and develop potential range maps for individual species of trees, shrubs and perennial flowers." They are looking for volunteers from both Canada and the United States.

There isn't much information available about the hardiness zone conversions for this area. This was a study reported in December 2008 about the creation of global hardiness zones. The maps are located halfway down the article.

This map shows higher zones than the accepted USDA map allows for - the USDA hardiness map simply assigns Zone 11 for anywhere with an average annual minimum temperature above 40 F. If they are following the zone system, then each zone is 10 F higher than the last one, making Zone 12 at 50 F and Zone 13 at 60 F.

If you live in the West, you should also know your Sunset garden zone. Sunset magazine has done research to more closely pinpoint the different growing climates of the region. Many nurseries and garden centers will use the Sunset zones as a reference, and these numbers will be used in the Sunset Western Garden Book instead of the USDA hardiness zones.